HQ exposure accelerates neutrophil maturation steps in bone marrow, leading to incomplete granulopoiesis (Hazel et al., 1995, Hazel et al., 1996a and Hazel et

al., 1996b), and in more severe toxicity, HQ damages bone marrow cells, impairing white and red blood cell production and maturation (Wiemels and Smith, 1999, Hazel et al., 1996a and Hazel et al., 1996b). In this latter condition, drastic reduction in the circulating cell numbers is detected, which contributes to anemia and immunosuppression observed in the intoxications (Lee et al., 2010 and Kim et al., 2005). Our data showing that HQ exposure did not affect the blood leukocyte profile after LPS inhalation, suggest that upon infection HQ exposure did not affect the neutrophil mobilization from Selleckchem AZD6244 the bone marrow. Nevertheless, neutrophil migration into alveolar space was impaired, as indicated by the reduced number of neutrophils recovered in BALF after LPS inhalation in mice upon HQ exposure. Interestingly, as lung MPO activity was significantly increased, we hypothesize that HQ exposure hampers cell transmigration from the lung microvascular vessels into the alveolar compartment.

MPO activity is an indirect marker of neutrophil presence at the injured site (Gosemann et al., 2010). It is worth mentioning that HQ stimulates MPO expression and EPZ015666 in vitro activity, and it is then endogenously metabolized by MPO to more reactive quinones (McGregor, 2007, Snyder, 2002 and Subrahmanyam et al., 1991). Overall, our findings revealing elevated lung MPO activity does not reflect a direct action of HQ on MPO metabolic system, since HQ exposure did not alter MPO activity in other relevant tissues with respect

to HQ toxicity, such as bone marrow and hepatic cells (data not shown). Neutrophil migration into inflamed areas depends on a diversity of chemical mediators secreted by resident and migrated cells at the inflamed site, and by membrane Glycogen branching enzyme receptors expressed on leukocytes and endothelial cells (Ley et al., 2007). While cytokines display pleiotropic actions, adhesion molecules exert specific actions on pathways of leukocyte migration. In our model, in vivo exposure to HQ did not affect the secretory activity of resident inflammatory cells and the adhesive functions of the microvascular endothelium. Of interest, the synthesis of cytokines and endothelial adhesion molecules depends on the transcriptional activation of the nuclear factor κB (NF-κB) ( Lawrence, 2009). Although the inhibitory action on this pathway is involved in BZ and HQ toxicity ( Choi et al., 2008, Ma et al., 2003 and Kerzic et al., 2003), it seems that the schedule of HQ exposure employed in this study did not affect this intracellular pathway in the lung endothelium or resident cells.